Note: the relevant code for this project lives in the shapes directory and in scenegraph/ShapesScene.cpp

This a C++ parametric tessellator for cubes, cylinders, cones, and spheres.

Click here to see a quick video demo!

To run this code, you will need to download QT creator here: https://www.qt.io/download-qt-installer.

Then, you can simply open the project and click run! Make sure to navigate to the 3D canvas.

To store triangle meshes, I created the Triangle and TriMesh data structures in TriMesh.h.

struct Triangle {
    std::vector<int> vertexIndices;
    std::vector<glm::vec3> vertexNormals;
};

struct TriMesh {
    std::vector<glm::vec3> &vertices;
    std::vector<Triangle> &faces;
};

Storing vertex indices instead of the vertices themselves helps maintain consistency and reduce the size of the mesh.

For the most part, I favored composition over inheritance for this project. I factored out the circular base of the Cone and Cylinder into a CircleBase m_circleBase member variable, and added Tessellator m_tessellator utility to each shape as well.

Inheritance was helpful, however, in allowing the ShapeScene to keep track of a Shape m_shape that could be a Cube, Cylinder, Cone, or Sphere. The Shape class is a thin wrapper I created around OpenGLShape which allows setting tessellation parameters (vertical or horizontal tessellation levels) and has a pure virtual method initializeVertexData. Every class derived from Shape must implement theinitializeVertexData method in order to be rendered by OpenGL.

The class Tessellator implements functionality common to all or many shapes. It has the following methods:

std::vector<Triangle> tessellate(int gridWidth, int gridHeight);
std::vector<float> processTriMesh(TriMesh triMesh);
void setUncurvedMeshNormals(TriMesh triMesh);

The tessellate function will traverse a vertex grid and construct counter-clockwise ordered triangle faces.

The processTriMesh function converts a completed triangle mesh into the vector of floats representing vertices and normals that OpenGL requires.

And setUncurvedMeshNormals simplifies the process of setting normals for any uncurved surface, like the side of a cube or the base of a cylinder. It uses crossproducts to compute one normal for each face directly from the vertex positions. For curved surfaces, like a sphere or the side of a cyliner/cone, the 3 vertices of a face will have different normals, so we instead use parametric calculations to compute the normals separately.